Abnormally Surface freshening and halocline deepening during 2006-2012 in the Canada Basin associated with Arctic Oscillation

The Canada Basin (CB) is undergoing significant changes which potentially impact the global climate change, since the CB is the important reservoir of the Pacific Water and liquid freshwater in the Arctic Ocean. The interannual variabilities of water mass in the CB in summer including surface freshwater and halocline from 2003-2017 are investigated. According to the hydrographic observation, abnormally surface freshening up to 2.75 PSU and halocline deepening up to 36 m in the CB are observed during 2006-2012, which are proved to be tightly associated with the Arctic Oscillation (AO). The AO index in early summer during 2006 to 2012 becomes negative and high. The strengthened easterly wind over the southern CB associated with the high negative AO index enhances the offshore Ekman transport to bring warm water off the southern coastal shelf into the CB, which accelerates sea ice melting and freshens surface water. The estimated warming magnitude during 2006-2012 associated with the negative AO is 1.5 times larger than that from the global warming in the last 15 years. The anticyclonic wind curl strengthening and ice retreat during 2006-2012 can both enhance the Ekman pumping to deepen the halocline in the CB, accounting for 32% and 68%, respectively. This work emphasizes the significant contribution of the interannual variability to the CB changes, which can help us to understand the air-sea-ice system in the CB and improve the prediction of its variations.